3,650 research outputs found
Opportunities for farming in alpine countries – pathways to truly grassland-based beef and milk production in Austria and Switzerland
Farming in the alpine countries of Austria and Switzerland fulfils important economic, socio-cultural and ecological functions for society. However, even though both Austria and Switzerland have increasingly focused their agricultural policy towards ecology, in both countries negative environmental impacts of agriculture still have to be reduced massively
Wavelet tomography of the Galactic magnetic field. I. The method
We suggest a two-dimensional wavelet devised to deduce the large-scale
structure of a physical field (e.g., the Galactic magnetic field) from its
integrals along straight paths from irregularly spaced data points to a fixed
interior point (the observer). The method can be applied to the analysis of
pulsar rotation and dispersion measures in terms of the large-scale Galactic
magnetic field and electron density. The method does not use any 'a priori'
assumptions about the physical field and can be considered as an algorithm of
wavelet differentiation. We argue that a certain combination of the wavelet
transformation with model fitting would be most efficient in the interpretation
of the available pulsar RM data.Comment: 8 pages, 12 Postscript figures, submitted to A&
Classification of images of wheat, ryegrass and brome grass species at early growth stages using principal component analysis
Wheat is one of the most important crops in Australia, and the identification of young plants is an important step towards developing an automated system for monitoring crop establishment and also for differentiating crop from weeds. In this paper, a framework to differentiate early narrow-leaf wheat from two common weeds from their digital images is developed. A combination of colour, texture and shape features is used. These features are reduced to three descriptors using Principal Component Analysis. The three components provide an effective and significant means for distinguishing the three grasses. Further analysis enables threshold levels to be set for the discrimination of the plant species. The PCA model was evaluated on an independent data set of plants and the results show accuracy of 88% and 85% in the differentiation of ryegrass and brome grass from wheat, respectively. The outcomes of this study can be integrated into new knowledge in developing computer vision systems used in automated weed management
Nutztierhaltung in den Alpenländern: Wege zu einer graslandbasierten Milch- und Fleischproduktion
Die Landwirtschaft erfüllt für die Gesellschaft wichtige wirtschaftliche, soziokulturelle und ökologische Funktionen. Gleichwohl hat sie starke negative Auswirkungen auf den Zustand der Ökosysteme. Daran konnte auch die Ökologisierung der Agrarpolitik seit Anfang der 1990er Jahre nicht prinzipiell etwas ändern. Aufgrund der großen Bedeutung von Grünland für die Landwirtschaft in der Schweiz (60 % der landwirtschaftlichen Nutzfläche) und Österreich (40 %) ist die Rolle der Wiederkäuer für eine ökologisch nachhaltige Agrar- und Ernährungspolitik besonders wichtig. Vor diesem Hintergrund haben wir analysiert, inwieweit standortgerechte, graslandbasierte regenerative Milch- und Rindfleischsysteme, die den Wettbewerb zwischen Lebens- und Futtermittelproduktion minimieren, zu einer ökologisch nachhaltigen Landnutzung beitragen können, ohne dabei die regionalen Ökosystemgrenzen zu überschreiten (Stolze et al. 2019)
Structures in the RM sky
Coherent structures in the distribution of the Faraday rotation measure of
extragalactic radio sources are isolated using wavelet transformation
technique. Signatures of the magnetic fields in the local (Orion) spiral arm,
the Sagittarius and Carina arms, the synchrotron Loop I and, possibly, the
Perseus arm have been revealed using the RM catalogues of Simard-Normandin et
al. (1981, 551 source)and Broten et al. (1988, 663 sources). Unlike earlier
analyses of the RM sky, our approach has allowed us to assess the stability of
the results with respect to modifications of the data sample.
We estimate the mean magnetic field strength in the Orion arm as 1.4\pm0.3
mkGauss and find clear indication of a magnetic field reversal at a distance of
0.6-1 kpc towards the Galactic centre. Our analysis has revealed for the first
time the extension of the reversal in the Carina arm. The direction of magnetic
field in the Perseus arm is reversed with respect to that in the Orion arm. The
average pitch angle of magnetic field in the nearby spiral arms is 15^\circ,
and the mean field strength in the Sagittarius-Carina and Perseus arms is
1.7\pm0.3 mkGauss and 1.4\pm1.2 mkGauss, respectively. The line-of-sight
magnetic field in Loop I is estimated as 0.9\pm0.3 mkGauss. We find firm
evidence of a dominant even symmetry of the local mean field with respect to
the galactic equator.Comment: 16 pages (LaTEX), 11 figures (eps), accepted for publication in MNRAS
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Comparison of different methods of measuring angle of progression in prediction of labor outcome
Objective: First, to compare the manual sagittal and para-sagittal and automated para-sagittal methods of measuring the angle of progression (AOP) by transperineal ultrasound during labor, and second, to develop models for the prediction of time-to-delivery and need for cesarean section (CS) for failure to progress (FTP) in a population of patients undergoing induction of labor.
Methods: This was a prospective observational study of transperineal ultrasound on a cohort of 512 women with singleton pregnancies undergiong induction of labor. A random selection of 50 stored images was assessed for inter- and intra-observer reliability between methods. In the cases of vaginal delivery univariate linear, multivariate linear and quantile regression were performed to predict time-to-delivery. Univariate and multivariate binomial logistic regression were performed to predict CS for FTP in the first stage of labor.
Results: The intra correlation coefficients (ICC) for the manual para-sagittal method for a single observer was 0.97 (CI 0.95-0.98) and for two observers was 0.96 (CI 0.93-0.98) indicating good reliability. The ICC for the sagittal method for a single observer was 0.93 (0.88-0.96) and for two observers was 0.74 (0.58-0.84) indicating moderate reliabilty for a single observer and poor reliability between two observers. Bland-Altman analysis demonstrated narrower limits of agreement for the manual para-saggittal approach than for the sagittal approach for both single and two observers. The automated para-sagittal method failed to capture an image in 19% of cases. The mean difference between sagittal and para-sagittal methods was 110. In pregnancies resulting in vaginal delivery, 54% of the variation in time-to-delivery was explained in a model combining parity, epidural and syntocinon use during labour and the sonographic findings of fetal head position and AOP. In the prediction of CS for FTP in the first stage of labour a model which combined maternal factors with the sonographic measurements of AOP and estimated fetal weight was superior to one utilising maternal factors alone (area under the curve 0.80 vs 0.76).
Conclusions: First, the method of measuring AOP with greatest reliability is the manual parasagittal technique and future research should focus on this technique, second, over half of the variation in time to vaginal delivery can be explained by a model that combines maternal factors, pregnancy characteristics and ultrasound findings, and third, the ability of AOP to provide clinically useful prediction CS for FTP in the first stage of labour is limited
Faraday caustics: Singularities in the Faraday spectrum and their utility as probes of magnetic field properties
We describe singularities in the distribution of polarized intensity as a
function of Faraday depth (i.e. the Faraday spectrum) caused by line-of-sight
(LOS) magnetic field reversals. We call these features Faraday caustics because
of their similarity to optical caustics. They appear as sharply peaked and
asymmetric profiles in the Faraday spectrum, that have a tail that extends to
one side. The direction in which the tail extends depends on the way in which
the LOS magnetic field reversal occurs (either changing from oncoming to
retreating or vice versa). We describe how Faraday caustics will form
three-dimensional surfaces that relate to boundaries between regions where the
LOS magnetic field has opposite polarity. We present examples from simulations
of the predicted polarized synchrotron emission from the Milky Way. We derive
either the probability or luminosity distribution of Faraday caustics produced
in a Gaussian magnetic field distribution as a function of their strength, F,
and find that for strong Faraday caustics P(F)\proptoF^{-3} . If fully
resolved, this distribution is also shown to depend on the Taylor microscale,
which relates to the largest scale over which dissipation is important in a
turbulent flow.Comment: 14 pages, 9 figures, Accepted for publication in Astronomy &
Astrophysic
On limits of spacetimes -- a coordinate-free approach
A coordinate-free approach to limits of spacetimes is developed. The limits
of the Schwarzschild metric as the mass parameter tends to 0 or are
studied, extending previous results. Besides the known Petrov type D and 0
limits, three vacuum plane-wave solutions of Petrov type N are found to be
limits of the Schwarzschild spacetime.Comment: 19 p
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